The first star catalog was made by the Greek astronomer, Hipparchos,
in 150 BC. He also created a system used to measure the
brightness of each star. He gave each star a magnitude
number. The brightest stars were magnitude 1. If they
were slightly fainter, they were magnitude 2 and so on, down to
magnitude 6.

Once the
telescope was invented, we could see objects fainter than magnitude
6. The scale had to be changed, so higher numbers were
added. For extremely bright objects, negative magnitudes were
added.

Every 5
magnitudes represent a change in magnitude or brightness of 100
times. For example, a magnitude 3 star is 100 times brighter
then a magnitude 8 star.